Equipment for joining portions of a continuous web of material to form a package are known in the art. Such seals can be formed by pressing together layers of a continuous web (or webs) while heating the layers, thereby bonding the layers of the web together. U.S. Pat. No. 5,220,771 issued Jun. 22, 1993 to Burns discloses a tetrahedronal packaging machine for packaging liquids. Burns discloses heat sealing jaws mounted on an endless chain for forming package seals. U.S. Pat. No. 3,585,623 issued Jun. 15, 1971 to Laukaitis discloses an open circuit detector for a heating element. The heating elements form part of a conveyor element in a packaging machine. Conveyor chains are provided to carry the package forming conveyor elements. Each conveyor element can include a knife and a recess for accepting the knife. Each knife is periodically actuated to chop between parallel heat seals to separate package units from each other. The Laukaitis apparatus suffers from the complexity that a heating element and knife are included on each of several conveyor elements.
Equipment for spacing and advancing packages along a path is also known in the art. U.S. Pat. No. 5,328,021 issued Jul. 12, 1994 to Calvert et al. discloses adjustable flight bars for advancing packages in sequence along a path. The distance between adjacent flight bars can be varied to make the system adaptable for use with packages of different horizontal dimension. U.S. Pat. No. 3,959,952issued Jun. 1, 1976 to Deutschlander discloses a packaging apparatus using a hose shaped wrapper containing uniformly spaced groups of articles to be packaged. The apparatus has cooperating rotating welding shoes disposed in the path of travel of the wrapper for forming transverse seams in the wall portions of the wrapper between two article groups. Articles in each group of articles are shown standing edgewise. A plurality of pressing members are secured to endless chains. Each pressing member on one chain cooperates with a pressing member on the other chain for pinching together the wrapper prior to passage of the wrapper through the welding shoes. The pressing members thereby prevent leading or trailing articles from toppling over within the wrapper. Deutschlander teaches that toppling of the articles can prevent subsequent formation of the transverse seams in the wrapper. However Deutschlander does not recognize or address the problem of seal separation after the wrapper passes through the welding shoes.
Accordingly, those engaged in packaging research and development continue the search for effective packaging systems that are not overly complex, yet provide consistent package quality. The present invention recognizes the need for a relatively simple yet dependable packaging system for heat sealing spaced groups of articles intermediate layers of a continuous wrapper, while preventing separation of the package seals prior to cutting the continuous wrapper to form discrete sealed packages of the articles. In particular, the present invention recognizes that when packaging compressible stacks of absorbent articles between layers of heat bonded thermoplastic film, expansion of the stack of absorbent articles can separate the heat seals bonding the film layers together.
Accordingly, it is an object of the present invention to provide a method and apparatus for sealing spaced groups of absorbent articles intermediate layers of a continuous wrapper.
Another object of the present invention is to provide a method and apparatus for supporting layers of a continuous wrapper as the wrapper is carried intermediate a wrapper seal apparatus and a wrapper seal cutting apparatus to thereby prevent separation of the wrapper seals.